mono/sgen/sgen-los.c

   1 /*
   2  * sgen-los.c: Large objects space.
   3  *
   4  * Author:
   5  *      Paolo Molaro (lupus@ximian.com)
   6  *
   7  * Copyright 2005-2010 Novell, Inc (http://www.novell.com)
   8  *
   9  * Thread start/stop adapted from Boehm's GC:
  10  * Copyright (c) 1994 by Xerox Corporation.  All rights reserved.
  11  * Copyright (c) 1996 by Silicon Graphics.  All rights reserved.
  12  * Copyright (c) 1998 by Fergus Henderson.  All rights reserved.
  13  * Copyright (c) 2000-2004 by Hewlett-Packard Company.  All rights reserved.
  14  * Copyright 2001-2003 Ximian, Inc
  15  * Copyright 2003-2010 Novell, Inc.
  16  * Copyright (C) 2012 Xamarin Inc
  17  *
  18  * This library is free software; you can redistribute it and/or
  19  * modify it under the terms of the GNU Library General Public
  20  * License 2.0 as published by the Free Software Foundation;
  21  *
  22  * This library is distributed in the hope that it will be useful,
  23  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  24  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  25  * Library General Public License for more details.
  26  *
  27  * You should have received a copy of the GNU Library General Public
  28  * License 2.0 along with this library; if not, write to the Free
  29  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  30  */
  31
  32 #include "config.h"
  33
  34 #ifdef HAVE_SGEN_GC
  35
  36 #include <string.h>
  37
  38 #include "mono/sgen/sgen-gc.h"
  39 #include "mono/sgen/sgen-protocol.h"
  40 #include "mono/sgen/sgen-cardtable.h"
  41 #include "mono/sgen/sgen-memory-governor.h"
  42 #include "mono/sgen/sgen-client.h"
  43
  44 #define LOS_SECTION_SIZE        (1024 * 1024)
  45
  46 /*
  47  * This shouldn't be much smaller or larger than MAX_SMALL_OBJ_SIZE.
  48  * Must be at least sizeof (LOSSection).
  49  */
  50 #define LOS_CHUNK_SIZE          4096
  51 #define LOS_CHUNK_BITS          12
  52
  53 /* Largest object that can be allocated in a section. */
  54 #define LOS_SECTION_OBJECT_LIMIT        (LOS_SECTION_SIZE - LOS_CHUNK_SIZE - sizeof (LOSObject))
  55 //#define LOS_SECTION_OBJECT_LIMIT      0
  56 #define LOS_SECTION_NUM_CHUNKS          ((LOS_SECTION_SIZE >> LOS_CHUNK_BITS) - 1)
  57
  58 #define LOS_SECTION_FOR_OBJ(obj)        ((LOSSection*)((mword)(obj) & ~(mword)(LOS_SECTION_SIZE - 1)))
  59 #define LOS_CHUNK_INDEX(obj,section)    (((char*)(obj) - (char*)(section)) >> LOS_CHUNK_BITS)
  60
  61 #define LOS_NUM_FAST_SIZES              32
  62
  63 typedef struct _LOSFreeChunks LOSFreeChunks;
  64 struct _LOSFreeChunks {
  65         LOSFreeChunks *next_size;
  66         size_t size;
  67 };
  68
  69 typedef struct _LOSSection LOSSection;
  70 struct _LOSSection {
  71         LOSSection *next;
  72         size_t num_free_chunks;
  73         unsigned char *free_chunk_map;
  74 };
  75
  76 LOSObject *los_object_list = NULL;
  77 mword los_memory_usage = 0;
  78
  79 static LOSSection *los_sections = NULL;
  80 static LOSFreeChunks *los_fast_free_lists [LOS_NUM_FAST_SIZES]; /* 0 is for larger sizes */
  81 static mword los_num_objects = 0;
  82 static int los_num_sections = 0;
  83
  84 //#define USE_MALLOC
  85 //#define LOS_CONSISTENCY_CHECK
  86 //#define LOS_DUMMY
  87
  88 #ifdef LOS_DUMMY
  89 #define LOS_SEGMENT_SIZE        (4096 * 1024)
  90
  91 static char *los_segment = NULL;
  92 static int los_segment_index = 0;
  93 #endif
  94
  95 mword
  96 sgen_los_object_size (LOSObject *obj)
  97 {
  98         return obj->size & ~1L;
  99 }
 100
 101 #ifdef LOS_CONSISTENCY_CHECK
 102 static void
 103 los_consistency_check (void)
 104 {
 105         LOSSection *section;
 106         LOSObject *obj;
 107         int i;
 108         mword memory_usage = 0;
 109
 110         for (obj = los_object_list; obj; obj = obj->next) {
 111                 mword obj_size = sgen_los_object_size (obj);
 112                 char *end = obj->data + obj_size;
 113                 int start_index, num_chunks;
 114
 115                 memory_usage += obj_size;
 116
 117                 if (obj_size > LOS_SECTION_OBJECT_LIMIT)
 118                         continue;
 119
 120                 section = LOS_SECTION_FOR_OBJ (obj);
 121
 122                 g_assert (end <= (char*)section + LOS_SECTION_SIZE);
 123
 124                 start_index = LOS_CHUNK_INDEX (obj, section);
 125                 num_chunks = (obj_size + sizeof (LOSObject) + LOS_CHUNK_SIZE - 1) >> LOS_CHUNK_BITS;
 126                 for (i = start_index; i < start_index + num_chunks; ++i)
 127                         g_assert (!section->free_chunk_map [i]);
 128         }
 129
 130         for (i = 0; i < LOS_NUM_FAST_SIZES; ++i) {
 131                 LOSFreeChunks *size_chunks;
 132                 for (size_chunks = los_fast_free_lists [i]; size_chunks; size_chunks = size_chunks->next_size) {
 133                         LOSSection *section = LOS_SECTION_FOR_OBJ (size_chunks);
 134                         int j, num_chunks, start_index;
 135
 136                         if (i == 0)
 137                                 g_assert (size_chunks->size >= LOS_NUM_FAST_SIZES * LOS_CHUNK_SIZE);
 138                         else
 139                                 g_assert (size_chunks->size == i * LOS_CHUNK_SIZE);
 140
 141                         num_chunks = size_chunks->size >> LOS_CHUNK_BITS;
 142                         start_index = LOS_CHUNK_INDEX (size_chunks, section);
 143                         for (j = start_index; j < start_index + num_chunks; ++j)
 144                                 g_assert (section->free_chunk_map [j]);
 145                 }
 146         }
 147
 148         g_assert (los_memory_usage == memory_usage);
 149 }
 150 #endif
 151
 152 static void
 153 add_free_chunk (LOSFreeChunks *free_chunks, size_t size)
 154 {
 155         size_t num_chunks = size >> LOS_CHUNK_BITS;
 156
 157         free_chunks->size = size;
 158
 159         if (num_chunks >= LOS_NUM_FAST_SIZES)
 160                 num_chunks = 0;
 161         free_chunks->next_size = los_fast_free_lists [num_chunks];
 162         los_fast_free_lists [num_chunks] = free_chunks;
 163 }
 164
 165 static LOSFreeChunks*
 166 get_from_size_list (LOSFreeChunks **list, size_t size)
 167 {
 168         LOSFreeChunks *free_chunks = NULL;
 169         LOSSection *section;
 170         size_t i, num_chunks, start_index;
 171
 172
 173         g_assert ((size & (LOS_CHUNK_SIZE - 1)) == 0);
 174
 175         while (*list) {
 176                 free_chunks = *list;
 177                 if (free_chunks->size >= size)
 178                         break;
 179                 list = &(*list)->next_size;
 180         }
 181
 182         if (!*list)
 183                 return NULL;
 184
 185         *list = free_chunks->next_size;
 186
 187         if (free_chunks->size > size)
 188                 add_free_chunk ((LOSFreeChunks*)((char*)free_chunks + size), free_chunks->size - size);
 189
 190         num_chunks = size >> LOS_CHUNK_BITS;
 191
 192         section = LOS_SECTION_FOR_OBJ (free_chunks);
 193
 194         start_index = LOS_CHUNK_INDEX (free_chunks, section);
 195         for (i = start_index; i < start_index + num_chunks; ++i) {
 196                 g_assert (section->free_chunk_map [i]);
 197                 section->free_chunk_map [i] = 0;
 198         }
 199
 200         section->num_free_chunks -= size >> LOS_CHUNK_BITS;
 201         g_assert (section->num_free_chunks >= 0);
 202
 203         return free_chunks;
 204 }
 205
 206 static LOSObject*
 207 get_los_section_memory (size_t size)
 208 {
 209         LOSSection *section;
 210         LOSFreeChunks *free_chunks;
 211         size_t num_chunks;
 212
 213         size += LOS_CHUNK_SIZE - 1;
 214         size &= ~(LOS_CHUNK_SIZE - 1);
 215
 216         num_chunks = size >> LOS_CHUNK_BITS;
 217
 218         g_assert (size > 0 && size - sizeof (LOSObject) <= LOS_SECTION_OBJECT_LIMIT);
 219         g_assert (num_chunks > 0);
 220
 221  retry:
 222         if (num_chunks >= LOS_NUM_FAST_SIZES) {
 223                 free_chunks = get_from_size_list (&los_fast_free_lists [0], size);
 224         } else {
 225                 size_t i;
 226                 for (i = num_chunks; i < LOS_NUM_FAST_SIZES; ++i) {
 227                         free_chunks = get_from_size_list (&los_fast_free_lists [i], size);
 228                         if (free_chunks)
 229                                 break;
 230                 }
 231                 if (!free_chunks)
 232                         free_chunks = get_from_size_list (&los_fast_free_lists [0], size);
 233         }
 234
 235         if (free_chunks)
 236                 return (LOSObject*)free_chunks;
 237
 238         if (!sgen_memgov_try_alloc_space (LOS_SECTION_SIZE, SPACE_LOS))
 239                 return NULL;
 240
 241         section = (LOSSection *)sgen_alloc_os_memory_aligned (LOS_SECTION_SIZE, LOS_SECTION_SIZE, (SgenAllocFlags)(SGEN_ALLOC_HEAP | SGEN_ALLOC_ACTIVATE), NULL);
 242
 243         if (!section)
 244                 return NULL;
 245
 246         free_chunks = (LOSFreeChunks*)((char*)section + LOS_CHUNK_SIZE);
 247         free_chunks->size = LOS_SECTION_SIZE - LOS_CHUNK_SIZE;
 248         free_chunks->next_size = los_fast_free_lists [0];
 249         los_fast_free_lists [0] = free_chunks;
 250
 251         section->num_free_chunks = LOS_SECTION_NUM_CHUNKS;
 252
 253         section->free_chunk_map = (unsigned char*)section + sizeof (LOSSection);
 254         g_assert (sizeof (LOSSection) + LOS_SECTION_NUM_CHUNKS + 1 <= LOS_CHUNK_SIZE);
 255         section->free_chunk_map [0] = 0;
 256         memset (section->free_chunk_map + 1, 1, LOS_SECTION_NUM_CHUNKS);
 257
 258         section->next = los_sections;
 259         los_sections = section;
 260
 261         ++los_num_sections;
 262
 263         goto retry;
 264 }
 265
 266 static void
 267 free_los_section_memory (LOSObject *obj, size_t size)
 268 {
 269         LOSSection *section = LOS_SECTION_FOR_OBJ (obj);
 270         size_t num_chunks, i, start_index;
 271
 272         size += LOS_CHUNK_SIZE - 1;
 273         size &= ~(LOS_CHUNK_SIZE - 1);
 274
 275         num_chunks = size >> LOS_CHUNK_BITS;
 276
 277         g_assert (size > 0 && size - sizeof (LOSObject) <= LOS_SECTION_OBJECT_LIMIT);
 278         g_assert (num_chunks > 0);
 279
 280         section->num_free_chunks += num_chunks;
 281         g_assert (section->num_free_chunks <= LOS_SECTION_NUM_CHUNKS);
 282
 283         /*
 284          * We could free the LOS section here if it's empty, but we
 285          * can't unless we also remove its free chunks from the fast
 286          * free lists.  Instead, we do it in los_sweep().
 287          */
 288
 289         start_index = LOS_CHUNK_INDEX (obj, section);
 290         for (i = start_index; i < start_index + num_chunks; ++i) {
 291                 g_assert (!section->free_chunk_map [i]);
 292                 section->free_chunk_map [i] = 1;
 293         }
 294
 295         add_free_chunk ((LOSFreeChunks*)obj, size);
 296 }
 297
 298 static int pagesize;
 299
 300 void
 301 sgen_los_free_object (LOSObject *obj)
 302 {
 303         SGEN_ASSERT (0, !obj->cardtable_mod_union, "We should never free a LOS object with a mod-union table.");
 304
 305 #ifndef LOS_DUMMY
 306         mword size = sgen_los_object_size (obj);
 307         SGEN_LOG (4, "Freed large object %p, size %lu", obj->data, (unsigned long)size);
 308         binary_protocol_empty (obj->data, size);
 309
 310         los_memory_usage -= size;
 311         los_num_objects--;
 312
 313 #ifdef USE_MALLOC
 314         free (obj);
 315 #else
 316         if (size > LOS_SECTION_OBJECT_LIMIT) {
 317                 if (!pagesize)
 318                         pagesize = mono_pagesize ();
 319                 size += sizeof (LOSObject);
 320                 size += pagesize - 1;
 321                 size &= ~(pagesize - 1);
 322                 sgen_free_os_memory (obj, size, SGEN_ALLOC_HEAP);
 323                 sgen_memgov_release_space (size, SPACE_LOS);
 324         } else {
 325                 free_los_section_memory (obj, size + sizeof (LOSObject));
 326 #ifdef LOS_CONSISTENCY_CHECKS
 327                 los_consistency_check ();
 328 #endif
 329         }
 330 #endif
 331 #endif
 332 }
 333
 334 /*
 335  * Objects with size >= MAX_SMALL_SIZE are allocated in the large object space.
 336  * They are currently kept track of with a linked list.
 337  * They don't move, so there is no need to pin them during collection
 338  * and we avoid the memcpy overhead.
 339  */
 340 void*
 341 sgen_los_alloc_large_inner (GCVTable vtable, size_t size)
 342 {
 343         LOSObject *obj = NULL;
 344         void **vtslot;
 345
 346         g_assert (size > SGEN_MAX_SMALL_OBJ_SIZE);
 347         g_assert ((size & 1) == 0);
 348
 349         /*
 350          * size + sizeof (LOSObject) <= SSIZE_MAX - (mono_pagesize () - 1)
 351          *
 352          * therefore:
 353          *
 354          * size <= SSIZE_MAX - (mono_pagesize () - 1) - sizeof (LOSObject)
 355          */
 356         if (size > SSIZE_MAX - (mono_pagesize () - 1) - sizeof (LOSObject))
 357                 return NULL;
 358
 359 #ifdef LOS_DUMMY
 360         if (!los_segment)
 361                 los_segment = sgen_alloc_os_memory (LOS_SEGMENT_SIZE, SGEN_ALLOC_HEAP | SGEN_ALLOC_ACTIVATE, NULL);
 362         los_segment_index = ALIGN_UP (los_segment_index);
 363
 364         obj = (LOSObject*)(los_segment + los_segment_index);
 365         los_segment_index += size + sizeof (LOSObject);
 366         g_assert (los_segment_index <= LOS_SEGMENT_SIZE);
 367 #else
 368         sgen_ensure_free_space (size);
 369
 370 #ifdef USE_MALLOC
 371         obj = malloc (size + sizeof (LOSObject));
 372         memset (obj, 0, size + sizeof (LOSObject));
 373 #else
 374         if (size > LOS_SECTION_OBJECT_LIMIT) {
 375                 size_t alloc_size = size;
 376                 if (!pagesize)
 377                         pagesize = mono_pagesize ();
 378                 alloc_size += sizeof (LOSObject);
 379                 alloc_size += pagesize - 1;
 380                 alloc_size &= ~(pagesize - 1);
 381                 if (sgen_memgov_try_alloc_space (alloc_size, SPACE_LOS)) {
 382                         obj = (LOSObject *)sgen_alloc_os_memory (alloc_size, (SgenAllocFlags)(SGEN_ALLOC_HEAP | SGEN_ALLOC_ACTIVATE), NULL);
 383                 }
 384         } else {
 385                 obj = get_los_section_memory (size + sizeof (LOSObject));
 386                 if (obj)
 387                         memset (obj, 0, size + sizeof (LOSObject));
 388         }
 389 #endif
 390 #endif
 391         if (!obj)
 392                 return NULL;
 393         g_assert (!((mword)obj->data & (SGEN_ALLOC_ALIGN - 1)));
 394         obj->size = size;
 395         vtslot = (void**)obj->data;
 396         *vtslot = vtable;
 397         sgen_update_heap_boundaries ((mword)obj->data, (mword)obj->data + size);
 398         obj->next = los_object_list;
 399         los_object_list = obj;
 400         los_memory_usage += size;
 401         los_num_objects++;
 402         SGEN_LOG (4, "Allocated large object %p, vtable: %p (%s), size: %zd", obj->data, vtable, sgen_client_vtable_get_name (vtable), size);
 403         binary_protocol_alloc (obj->data, vtable, size, sgen_client_get_provenance ());
 404
 405 #ifdef LOS_CONSISTENCY_CHECK
 406         los_consistency_check ();
 407 #endif
 408
 409         return obj->data;
 410 }
 411
 412 static void sgen_los_unpin_object (GCObject *data);
 413
 414 void
 415 sgen_los_sweep (void)
 416 {
 417         LOSObject *bigobj, *prevbo;
 418         LOSSection *section, *prev;
 419         int i;
 420         int num_sections = 0;
 421
 422         /* sweep the big objects list */
 423         prevbo = NULL;
 424         for (bigobj = los_object_list; bigobj;) {
 425                 SGEN_ASSERT (0, !SGEN_OBJECT_IS_PINNED (bigobj->data), "Who pinned a LOS object?");
 426
 427                 if (bigobj->cardtable_mod_union) {
 428                         sgen_card_table_free_mod_union (bigobj->cardtable_mod_union, (char*)bigobj->data, sgen_los_object_size (bigobj));
 429                         bigobj->cardtable_mod_union = NULL;
 430                 }
 431
 432                 if (sgen_los_object_is_pinned (bigobj->data)) {
 433                         sgen_los_unpin_object (bigobj->data);
 434                         sgen_update_heap_boundaries ((mword)bigobj->data, (mword)bigobj->data + sgen_los_object_size (bigobj));
 435                 } else {
 436                         LOSObject *to_free;
 437                         /* not referenced anywhere, so we can free it */
 438                         if (prevbo)
 439                                 prevbo->next = bigobj->next;
 440                         else
 441                                 los_object_list = bigobj->next;
 442                         to_free = bigobj;
 443                         bigobj = bigobj->next;
 444                         sgen_los_free_object (to_free);
 445                         continue;
 446                 }
 447                 prevbo = bigobj;
 448                 bigobj = bigobj->next;
 449         }
 450
 451         /* Try to free memory */
 452         for (i = 0; i < LOS_NUM_FAST_SIZES; ++i)
 453                 los_fast_free_lists [i] = NULL;
 454
 455         prev = NULL;
 456         section = los_sections;
 457         while (section) {
 458                 if (section->num_free_chunks == LOS_SECTION_NUM_CHUNKS) {
 459                         LOSSection *next = section->next;
 460                         if (prev)
 461                                 prev->next = next;
 462                         else
 463                                 los_sections = next;
 464                         sgen_free_os_memory (section, LOS_SECTION_SIZE, SGEN_ALLOC_HEAP);
 465                         sgen_memgov_release_space (LOS_SECTION_SIZE, SPACE_LOS);
 466                         section = next;
 467                         --los_num_sections;
 468                         continue;
 469                 }
 470
 471                 for (i = 0; i <= LOS_SECTION_NUM_CHUNKS; ++i) {
 472                         if (section->free_chunk_map [i]) {
 473                                 int j;
 474                                 for (j = i + 1; j <= LOS_SECTION_NUM_CHUNKS && section->free_chunk_map [j]; ++j)
 475                                         ;
 476                                 add_free_chunk ((LOSFreeChunks*)((char*)section + (i << LOS_CHUNK_BITS)), (j - i) << LOS_CHUNK_BITS);
 477                                 i = j - 1;
 478                         }
 479                 }
 480
 481                 prev = section;
 482                 section = section->next;
 483
 484                 ++num_sections;
 485         }
 486
 487 #ifdef LOS_CONSISTENCY_CHECK
 488         los_consistency_check ();
 489 #endif
 490
 491         /*
 492         g_print ("LOS sections: %d  objects: %d  usage: %d\n", num_sections, los_num_objects, los_memory_usage);
 493         for (i = 0; i < LOS_NUM_FAST_SIZES; ++i) {
 494                 int num_chunks = 0;
 495                 LOSFreeChunks *free_chunks;
 496                 for (free_chunks = los_fast_free_lists [i]; free_chunks; free_chunks = free_chunks->next_size)
 497                         ++num_chunks;
 498                 g_print ("  %d: %d\n", i, num_chunks);
 499         }
 500         */
 501
 502         g_assert (los_num_sections == num_sections);
 503 }
 504
 505 gboolean
 506 sgen_ptr_is_in_los (char *ptr, char **start)
 507 {
 508         LOSObject *obj;
 509
 510         *start = NULL;
 511         for (obj = los_object_list; obj; obj = obj->next) {
 512                 char *end = (char*)obj->data + sgen_los_object_size (obj);
 513
 514                 if (ptr >= (char*)obj->data && ptr < end) {
 515                         *start = (char*)obj->data;
 516                         return TRUE;
 517                 }
 518         }
 519         return FALSE;
 520 }
 521
 522 void
 523 sgen_los_iterate_objects (IterateObjectCallbackFunc cb, void *user_data)
 524 {
 525         LOSObject *obj;
 526
 527         for (obj = los_object_list; obj; obj = obj->next)
 528                 cb (obj->data, sgen_los_object_size (obj), user_data);
 529 }
 530
 531 gboolean
 532 sgen_los_is_valid_object (char *object)
 533 {
 534         LOSObject *obj;
 535
 536         for (obj = los_object_list; obj; obj = obj->next) {
 537                 if ((char*)obj->data == object)
 538                         return TRUE;
 539         }
 540         return FALSE;
 541 }
 542
 543 gboolean
 544 mono_sgen_los_describe_pointer (char *ptr)
 545 {
 546         LOSObject *obj;
 547
 548         for (obj = los_object_list; obj; obj = obj->next) {
 549                 const char *los_kind;
 550                 mword size;
 551                 gboolean pinned;
 552
 553                 if ((char*)obj->data > ptr || (char*)obj->data + sgen_los_object_size (obj) <= ptr)
 554                         continue;
 555
 556                 size = sgen_los_object_size (obj);
 557                 pinned = sgen_los_object_is_pinned (obj->data);
 558
 559                 if (size > LOS_SECTION_OBJECT_LIMIT)
 560                         los_kind = "huge-los-ptr";
 561                 else
 562                         los_kind = "los-ptr";
 563
 564                 if ((char*)obj->data == ptr) {
 565                         SGEN_LOG (0, "%s (size %d pin %d)\n", los_kind, (int)size, pinned ? 1 : 0);
 566                 } else {
 567                         SGEN_LOG (0, "%s (interior-ptr offset %zd size %d pin %d)",
 568                                         los_kind, ptr - (char*)obj->data, (int)size, pinned ? 1 : 0);
 569                 }
 570
 571                 return TRUE;
 572         }
 573         return FALSE;
 574 }
 575
 576 void
 577 sgen_los_iterate_live_block_ranges (sgen_cardtable_block_callback callback)
 578 {
 579         LOSObject *obj;
 580         for (obj = los_object_list; obj; obj = obj->next) {
 581                 GCVTable vt = SGEN_LOAD_VTABLE (obj->data);
 582                 if (SGEN_VTABLE_HAS_REFERENCES (vt))
 583                         callback ((mword)obj->data, sgen_los_object_size (obj));
 584         }
 585 }
 586
 587 static guint8*
 588 get_cardtable_mod_union_for_object (LOSObject *obj)
 589 {
 590         mword size = sgen_los_object_size (obj);
 591         guint8 *mod_union = obj->cardtable_mod_union;
 592         guint8 *other;
 593         if (mod_union)
 594                 return mod_union;
 595         mod_union = sgen_card_table_alloc_mod_union ((char*)obj->data, size);
 596         other = (guint8 *)SGEN_CAS_PTR ((gpointer*)&obj->cardtable_mod_union, mod_union, NULL);
 597         if (!other) {
 598                 SGEN_ASSERT (0, obj->cardtable_mod_union == mod_union, "Why did CAS not replace?");
 599                 return mod_union;
 600         }
 601         sgen_card_table_free_mod_union (mod_union, (char*)obj->data, size);
 602         return other;
 603 }
 604
 605 void
 606 sgen_los_scan_card_table (gboolean mod_union, ScanCopyContext ctx)
 607 {
 608         LOSObject *obj;
 609
 610         for (obj = los_object_list; obj; obj = obj->next) {
 611                 guint8 *cards;
 612
 613                 if (!SGEN_OBJECT_HAS_REFERENCES (obj->data))
 614                         continue;
 615
 616                 if (mod_union) {
 617                         if (!sgen_los_object_is_pinned (obj->data))
 618                                 continue;
 619
 620                         cards = get_cardtable_mod_union_for_object (obj);
 621                         g_assert (cards);
 622                 } else {
 623                         cards = NULL;
 624                 }
 625
 626                 sgen_cardtable_scan_object (obj->data, sgen_los_object_size (obj), cards, mod_union, ctx);
 627         }
 628 }
 629
 630 void
 631 sgen_los_count_cards (long long *num_total_cards, long long *num_marked_cards)
 632 {
 633         LOSObject *obj;
 634         long long total_cards = 0;
 635         long long marked_cards = 0;
 636
 637         for (obj = los_object_list; obj; obj = obj->next) {
 638                 int i;
 639                 guint8 *cards = sgen_card_table_get_card_scan_address ((mword) obj->data);
 640                 guint8 *cards_end = sgen_card_table_get_card_scan_address ((mword) obj->data + sgen_los_object_size (obj) - 1);
 641                 mword num_cards = (cards_end - cards) + 1;
 642
 643                 if (!SGEN_OBJECT_HAS_REFERENCES (obj->data))
 644                         continue;
 645
 646                 total_cards += num_cards;
 647                 for (i = 0; i < num_cards; ++i) {
 648                         if (cards [i])
 649                                 ++marked_cards;
 650                 }
 651         }
 652
 653         *num_total_cards = total_cards;
 654         *num_marked_cards = marked_cards;
 655 }
 656
 657 void
 658 sgen_los_update_cardtable_mod_union (void)
 659 {
 660         LOSObject *obj;
 661
 662         for (obj = los_object_list; obj; obj = obj->next) {
 663                 if (!SGEN_OBJECT_HAS_REFERENCES (obj->data))
 664                         continue;
 665                 sgen_card_table_update_mod_union (get_cardtable_mod_union_for_object (obj),
 666                                 (char*)obj->data, sgen_los_object_size (obj), NULL);
 667         }
 668 }
 669
 670 LOSObject*
 671 sgen_los_header_for_object (GCObject *data)
 672 {
 673 #if _MSC_VER
 674         return (LOSObject*)((char*)data - (int)(&(((LOSObject*)0)->data)));
 675 #else
 676         return (LOSObject*)((char*)data - sizeof (LOSObject));
 677 #endif
 678 }
 679
 680 void
 681 sgen_los_pin_object (GCObject *data)
 682 {
 683         LOSObject *obj = sgen_los_header_for_object (data);
 684         obj->size = obj->size | 1;
 685         binary_protocol_pin (data, (gpointer)SGEN_LOAD_VTABLE (data), sgen_safe_object_get_size (data));
 686 }
 687
 688 static void
 689 sgen_los_unpin_object (GCObject *data)
 690 {
 691         LOSObject *obj = sgen_los_header_for_object (data);
 692         obj->size = sgen_los_object_size (obj);
 693 }
 694
 695 gboolean
 696 sgen_los_object_is_pinned (GCObject *data)
 697 {
 698         LOSObject *obj = sgen_los_header_for_object (data);
 699         return obj->size & 1;
 700 }
 701
 702 void
 703 sgen_los_mark_mod_union_card (GCObject *mono_obj, void **ptr)
 704 {
 705         LOSObject *obj = sgen_los_header_for_object (mono_obj);
 706         guint8 *mod_union = get_cardtable_mod_union_for_object (obj);
 707         size_t offset = sgen_card_table_get_card_offset ((char*)ptr, (char*)sgen_card_table_align_pointer ((char*)obj));
 708         SGEN_ASSERT (0, mod_union, "FIXME: optionally allocate the mod union if it's not here and CAS it in.");
 709         SGEN_ASSERT (0, (char*)obj == (char*)sgen_card_table_align_pointer ((char*)obj), "Why are LOS objects not card aligned?");
 710         mod_union [offset] = 1;
 711 }
 712
 713 #endif /* HAVE_SGEN_GC */